Project Summary: Neural mechanisms of live joint attention in autism spectrum disorders: an fNIRS hyperscanning investigation Autism spectrum disorder is a prevalent disorder affecting 1 in 68 children worldwide, with significant mental and emotional toll on patients and their families. The biological basis of these disorders is still unknown, but deficits in initiating and responding to joint attention are one of the earliest signs and predict later difficulties with language and social cognition. Thus far, joint attention has largely been studied using neuroimaging of solo individuals as they engage in these tasks. However, recent studies support the hypothesis that specialized neural mechanisms are recruited during live interactions between people that cannot be detected with traditional single subject experiments. These specialized mechanisms may play a role in disorders of social communication such as autism. Functional near-infrared spectroscopy (fNIRS) can be used to detect the brain activity from two individuals as they engage in a social interaction. This proposal aims to design and implement a novel joint attention paradigm using fNIRS in which two people are facing each other and engaging in the task, enabling an analysis of what neural mechanisms are unique to a live social interaction compared to interactions with videos or non-social cues, and how these mechanisms are altered in the brains of people with autism. The first aim is to develop a novel, two-person paradigm to study joint attention during live interaction between two people. This will necessitate the design of a two-person experiment with a live interaction condition as well as conditions using non-responsive face videos and an arrow as a non-social cue to direct the attention. The second aim is to examine the differences in the neural circuitry of individuals with autism as they engage in live social interactive joint attention tasks with a neurotypical partner. Brain activity detected using fNIRS will be determined for a live partner cue versus non-responsive and non-social cues. Areas that show greater brain activity during the live social interaction in typical adults will be analyzed in adults with autism to asses whether neural responses to live interaction are fundamentally altered in people with this disorder. The third aim is to analyze the coherence in response to rapid interaction cues between the brains of two individuals during live joint attention. Wavelet analysis will be used to determine what brain areas show increased coherence across paired individuals during the live interaction compared to the other conditions. Areas that show increased coherence in pairs of typical individuals will provide a hypothesis for testing coherence between pairs when one individual has autism. Evidence for neural mechanisms specific to live joint attention that are altered in autism will provide important advances in understanding the fundamental basis of this disorder.